The present invention relates to point of use water filtration systems employed in purifying household drinking and tap water. In particular, the present invention relates to a feeder insert for a water filtration cartridge. The insert contains additional purification substances from those contained in the filtration cartridge for release into the household water supply by the insert to further purify the water flowing through the filtration cartridge. The feeder insert can also contain chemicals to be released into the water supply that perform functions other than water purification, such as phosphate descaling agents.
Prior art point of use water filtration systems remove water-borne contaminants in generally the same way. They employ a housing comprised of a sump, a hollow, tubular filtration cartridge contained within the sump and an inlet/outlet cap detachably mounted to the sump. The incoming water to be filtered flows into the system housing through the inlet of the cap and down into the sump containing the filter cartridge. The water then flows radially through the filtration cartridge, contacting the purification substance held within the filtration cartridge to remove the contaminants present in the water. Upon exiting the interior surface of the filtration cartridge, the water enters a central, axial chamber defined by the filtration cartridge. The water flows upward along this chamber through the upper end of the filtration cartridge to an outlet from the system located at the outlet end of the cap.
While most point of use water filtration systems employ this general mechanism, the exact process and purification substance by which the contaminants are removed in the filtration cartridge differ from system to system. Some systems employ a simple pleated paper filter located within the filtration cartridge to remove the water-borne contaminants present in the water. Others employ a semi-permeable membrane located in the filter cartridge for use in a reverse osmosis process to remove the contaminants. Other systems employ activated carbon either in block or granular form within the filtration cartridge as the main ingredient for removing the contaminants.
Regardless of the material used for removing the water-borne contaminants in the filtration cartridge, a problem still exists when a large amount of potentially harmful organisms including bacteria, viruses and other microbes are present within the household water supply. Most of these filtration substances are able to remove the majority of bacteria and microbes present in the water supply, but they are unable to remove them completely and are also unable to remove any of certain types of these organisms, namely viruses, that may be present. In order to reduce the severity of this problem with microbial contaminants, one can incorporate an additional filter containing another purification substance in addition to the substance already present within the filtration system filter cartridge. It is well known in the prior art to place these additional filters within the central, axial chamber defined by the filtration cartridge. Some of the additional filters are formed of the same purification substance contained within the filtration cartridge in order to provide a second, identical filtration mechanism to remove the contaminants which remain in the water supply after the first filtration mechanism. While further reducing the amount of certain organic contaminants, such as the bacteria and microbes present with the water supply, if these filters employ the same materials as the filtration cartridge, they serve to lessen the amounts present, but not to remove them entirely.
Other filtration systems employ a purification substance different from that contained in the filtration cartridge to perform a second filtration function on the water flowing through the filtration cartridge. The filtration system of U.S. Pat. No. 5,252,206 employs a ceramic inner filter disposed within a filtration cartridge containing a carbon block outer filter. The ceramic inner filter, with its small pore size, serves to capture and retain bacteria and other particulate contaminants that remain in the water supply after the water is filtered through the carbon block outer filter. The ceramic filter extends along the entire length of the central, axial chamber defined by the filtration cartridge. However, while this type of combination filter does effect the increased removal of microbial contaminants from the water supply, it does so with certain limitations. The ceramic filter tends to collect the dead microbes on its outside surface and hence must be periodically removed and cleaned in order for the filter to maintain its microbial filtration activity.
In order to prevent this bacterial buildup on the outside surface of the ceramic filter, U.S. Pat. No. 5,164,085 discloses a inner ceramic filter impregnated with silver, a well known bacteriocidal agent. However, even with this improved microorganism removal due to the presence of silver within the ceramic filter, the complete removal of bacteria, viruses and other microorganisms still cannot be achieved. Very small viruses are able to pass unhindered through the pores of the ceramic filter and remain in the water supply. Also the amount of silver that is impregnated in the ceramic filter is usually less than that required for complete removal of any microbes present in the water supply. This is due to the fact that the amount required for a complete microbial kill is above the maximum safe level for silver allowed to be present in a household water supply.
In response to this limitation, U.S. Pat. No. 5,273,650 discloses a multi-media filter able to overcome the limitations present in the prior art concerning the maximum amount of silver or silver compounds able to be impregnated within a ceramic filter used in a point of use water filtration system. The filter employs a ceramic pre-filter located in the position where prior art filtration systems utilizes the carbon block filtration cartridge. This ceramic pre-filter contains within its central core a halogenated purification resin. Incoming, unpurified water flows through the ceramic pre-filter removing some of the microbes present with the water supply, and then contacts the halogenated resin. This resin effects an instantaneous microbiocidal kill on the remaining microbes present in the water supply. Furthermore, if any microbes should happen to survive passage through the halogenated resin, the resin leaves residual iodine, or any other halogen used, in the water supply allowing for a continued microbiocidal effect downstream from the halogenated resin and through the outlet portion of the filtration system. The amount of resin present with the central core of the ceramic pre-filter can also be adjusted through using a filler rod disposed in the bottom of the central core. The filler rod can be made any length, reducing the space available for the resin in the central core and, thus, allowing for adjustment of the amount of resin available to respond to differing amounts of microbes present in a particular water supply. While this system overcomes the limitations on microbiocidal effects due to reduced amounts of silver allowable in ceramic filters found in the prior art, the ceramic pre-filter still needs to be removed to clean off the bacteria and microbes which collect on its exterior surface to allow for the pre-filter to function normally.
U.S. Pat. No. 5,061,367 discloses a cylindrical water filtration cartridge for use in a household point of use water filtration system which contains a halogenated resin outer filter and an activated carbon inner filter disposed with a central core formed by the outer halogenated resin filter. Water flowing into the cartridge first contacts the halogenated resin, effecting a complete microbial kill of any bacteria or microbes present within the household water supply. The water then flows into the activated carbon filter for removal of any metals or other particulate matter suspended within the water supply. The cartridge also allows for varying amounts of halogenated resin to be contained within the cartridge. One way in which this adjustment is accomplished is through the use of a buffering resin present within the cartridge below the halogenated resin to both reduce the amount of halogenated resin available by taking up space within the cartridge and also to prevent highly alkaline water supplies from unnecessarily increasing the release of the microbiocidal halogens from the halogenated resin. Another method employed to effect the adjustment of the amount of halogenated resin present in the cartridge utilizes a scavenger resin. Located above a halogenated resin within the cartridge, this scavenger resin serves to reclaim any excess halogen released into the water supply by the halogenated resin, thus reducing any harmful or unpleasant effects to the ultimate consumers that may be caused by excess halogens present in a water supply system. By employing the halogenated resin as a microbiocidal agent, this invention eliminates the need for a ceramic filter and thus eliminates the problems of the prior art ceramic filters with respect to silver content and microbe collections on the exterior surface of the ceramic filters. However, this invention does have a significant limitation in that the adjustment of the amount of halogenated resin present in the cartridge available to effect a microbiocidal kill on any microbiological material present within the water supply is not easily accomplished. In order to adjust the level of halogenated resin present, the entire cartridge must be removed and replaced with a separate cartridge containing a different amount of halogenated resin.